The present embodiments relate to providing image support to a practitioner in an interventional treatment of a target area in a patient.
Minimally invasive interventions with medical instruments, such as catheters, open up new possibilities that are easier for the patient to endure for the treatment of pathologies/lesions, such as aneurysms, for example. In order to be able to monitor the path of the medical instrument and/or the progression of treatment, it has already been suggested that interventional (e.g., minimally invasive procedures) may be carried out with image monitoring. For this purpose, fluoroscopy is generally used, which provides that X-ray images are taken with an X-ray device, for which a rather lower dose of X-rays is selected.
A further important aid to image support in an interventional procedure in the patient's vascular system is subtraction angiography. This involves a contrast agent that is clearly visible in the X-ray image being administered into the patient's circulation. By subtraction of a masked image acquired without contrast agent from an X-ray image with at least some blood vessels filled with contrast agent (e.g., a contrast-filled image), a subtraction angiogram that shows only the regions filled with contrast agent (e.g., the blood vessels) may be obtained. If projection images are acquired in various projection directions and methods of reconstruction are used, in the context of subtraction angiography, a three-dimensional subtraction angiography image (e.g., a three-dimensional subtraction angiography data set) may be obtained, and therefore, a three-dimensional image of the patient's vascular system may be obtained. Such three-dimensional image data sets may be used, for example, in the context of the navigation of medical instruments when for example, the three-dimensional subtraction angiography data set is registered with the system of coordinates of a position-defining device for the medical instrument.
Using subtraction angiography in fluoroscopic monitoring is likewise known. This likewise involves a masked image acquired without contrast agent being subtracted from an X-ray image taken using contrast agent (e.g., a filled image) in order to ultimately obtain the fluoroscopic image that is to be used for monitoring.
Problems always occur with fluoroscopic image monitoring of an interventional procedure when various blood vessels in the two-dimensional subtraction angiogram in the zone around the target area (e.g., the pathological feature) are superimposed, which may not generally be avoided, however. In order to be able to estimate the target area correctly, the person carrying out the intervention changes the projection direction, which in some cases may lead to important parts of the pathological feature no longer being shown with sufficient accuracy. Therefore, it is not possible to avoid a compromise, as far as the selection of the imaging geometry and consequently of the projection direction is concerned. The problem with superimpositions is, for example, that the allocation of blood vessels is not clear. If the target area is, for example, an aneurysm that is to be treated, in a blood vessel that is likewise to be seen in the two-dimensional projection image, it is not clear whether this blood vessel originates from the aneurysm or is not in contact with the aneurysm at all.